1. Field of the Invention
The present invention is directed to bags for transporting materials, in particular, to valve bags.
2. Background Art
A valve bag is a container having a body portion of substantially tubular configuration, which typically has an outer layer of at least one ply, and an inner layer of at least one ply. Typically the plies may be made from a relatively stiff and sturdy paper material. One end of the bag (usually the end the ultimate consumer opens) may be cut in a stepped end pattern, folded over and sealed, to form what is called a pinch-bottom bag. Alternatively, the end may be formed with two sets of flaps, arranged in opposed pairs. The first pair of opposed flaps are folded inwardly toward one another (in-folded flaps). The two other flaps (outer flaps), typically oriented perpendicular to the in-folded flaps, would be folded over the already folded flaps and glued in place to close that end of the bag, such that when the bag is filled, the bottom of the bag will assume a square-bottomed shape.
Rather than leave the opposite end of the bag completely open for filling by the manufacturer/purchaser of the unfinished bag, the bag end can be filled with the opposite (purchaser) end of the bag substantially closed, so long as a valve is provided. In a valved bag, the purchaser end is closed in the second manner described above. The tubular bag form is flattened somewhat, and the in-folded flaps correspond to the two opposite "short" sides of the bag. The in-folded flaps may or may not overlap. The outer flaps, which correspond to the "long" sides of the bag, are then folded over one another, and glued to each other. In addition, one of the in-folded flaps may be glued to the outer flaps. The remaining in-folded flap is not glued to either the outer flaps or the other in-folded flap, and so a channel can be formed, upon outward deflection of the glued and overlapped outer flaps, leading to the interior of the bag. If the in-folded flaps overlap, the valve is located on the side of the "under" flap. Filling can be accomplished by the insertion of an appropriately configured nozzle, which will extend to the gap between the in-folded flaps, to drop material into the interior of the bag, or if the in-folded flaps overlap, the nozzle will project under the "over" flap and into the bag far enough to clear the "under" flap and access the interior of the bag.
There are two general kinds of valved bags, those which cannot be sealed, and those which can be sealed. The bag previously described, is an unsealed bag, as once filling has been accomplished, there can be no further gluing, or other sealing procedure which can be done without potentially disturbing or contaminating the contents of the bag, since the gap between the outer flaps and the unglued in-folded flap would have to be re-opened to place a seal between them.
To help prevent sifting outwardly from such bags, a lining material, typically a soft polyethylene film, is placed in the interior of the valve region. The film is generally formed as a short tube, and is configured such that the film extends toward the opposite side of the bag farther than the adjacent in-folded flap, such that the contents will press against the film, pushing the film against the outer flap, and precluding sifting, particularly when the bag is laid on its side or inverted. Such a bag is exemplified by the Film-loc valve bag, manufactured by Stone Container Corporation. While sifting, dusting and spillage are not eliminated by such a bag, the losses are substantially reduced to a level acceptable for many uses of such bags. Neither are such bags fully sealed, against infiltration of material from the outside into the interior of the bag.
In some instances, it is desirable to be able to fully seal the bag, after filling by the valve method. Accordingly, an outwardly extending valve tube has been provided in some prior art bags, such as disclosed in Donini et al., U.S. Pat. No. 4,453,270. In such a bag, the valve extension is a tube, formed from the stiff paper bag material previously described. The tube is positioned inside the valve area, so as to extend outwardly, well past the side of the bag, and inwardly, to a position substantially even with the inner edge of the valve side in-folded flap. The inner surfaces of the tube are coated with an adhesive/sealing material, such as a heat activatable glue, or an adhesive which may be activated by ultrasonic means. During the filling process, the valve tube is opened, and a filling nozzle is inserted. Due the stiffness of the combined paper and sealing in the sealer, the valve tube may tend to remain slightly open, even after removal of the filling nozzle.
Once filled, the valve is typically flattened, and the end of the valve tube is sealed, either by application of heat or ultrasonic vibrations, to activate the sealing adhesive. In other valve tube bag constructions, a tab on the "upper" portion of the outwardly extending tube extends further than the "lower" portion, and instead of relying upon an adhesive lined tube, an applicator puts a hot melt glue on the underside of the tab, and a wiper presses the valve tube downward against the side of the filled bag, simultaneously closing the bag and affixing the tube against the bag side.
Prior art processes for filling and closing or sealing such bags having outwardly extending valve tubes involve the closing/sealing of the bags in the immediate vicinity of the packing apparatus which filled the bag. The bag is then transported from the location after closing and sealing. Such procedures, however, require that each packing apparatus be provided with its own sealing apparatus.
The trend in manufacturing processes now, however, particularly with extended valve tube bags, is not to provide one sealing apparatus per packing apparatus, since it requires less capital expense to use only one or two sealing apparatus for a packaging line, and the line speed can also be increased if common sealing apparatus are used for all the packing apparatus. The difficulty lies in that the filled, but unclosed and unsealed bags must be transported by conveyer to the sealing apparatus location. The bags may typically be dropped onto a conveyer.
Due to the stiffness of the valve tube material, as mentioned, the valve tube tends to remain open somewhat, as the bag is dropped onto the conveyer, leading to unacceptable spillage and dusting. In addition, the operation of the sealing apparatus may require that the bag be tipped from an upright position, to a position on its side, further leading to the possibility of dusting and spillage.
It is an object of the present invention, therefore to provide a valve bag construction, for sealable valve bags, which is suitable for efficient use in new packaging lines having only one or two sealing apparatus for a plurality of filling apparatus.
Still another object of the invention is to provide a valve bag construction for sealable valve bags, in which spillage and dusting can be controlled.
These and other objects of the invention will be come apparent in light of the present specification, claims and drawings.